I am trying out the path-based archive mode. I have a snap-synced mainnet node which was at the tip of the chain. I stopped it and first added just the --gcmode=archive flag, it indexed 90k blocks and I could query the last 90k states indeed.

I stopped the node once more and added --history.state=1000000 to extend the index range. It doesn't do any additional indexing. It said:

INFO [10-02|12:40:45.387] Enabled state history indexing
INFO [10-02|12:40:45.387] Initialized path database                triecache=614.00MiB statecache=409.00MiB buffer=256.00MiB state-history="last 1000000 blocks" index-history=true journal-dir=/home/ubuntu/datadir-geth/
geth/triedb
INFO [10-02|12:40:45.387] State histories have been fully indexed  last=5,369,269

But this was immediately on startup and I'm sure the node didn't do any work to index between 90k and 1m. Also trying out the API I don't see those states as available.